Monomer having diol structure, polymer thereof, and negative photoresist composition and pattern forming method using the same background of the invention

ABSTRACT

Disclosed is a negative photoresist which is suitable for use in photolithography using light of 220 nm or shorter like the light from the ArF excimer laser as exposure light, avoids pattern deformation originated from swelling and has a high adhesion strength to the substrate (a micro pattern is hard to be separated from the substrate) in addition to a dry etching resistance and high resolution. A negative photoresist composition contains a polymer having a diol structure having a repeating unit represented by a following formula (6), a crosslinking agent comprised of a compound containing a functional group represented by a following formula (12) and a photoacid generator which generates acid by exposure:

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a monomer having a diolstructure, a polymer thereof, and a negative photoresist composition anda pattern forming method using the same. More particularly, thisinvention relates to a monomer suitable as a material for a resist whichis used in photolithography in fabrication of various kinds ofsemiconductor devices using deep ultraviolet rays of 220 nm or shorter,particularly, light from an ArF excimer laser, as exposure light, apolymer thereof, and a negative photoresist composition and a patternforming method using the same.

[0003] 2. Description of the Related Art

[0004] Higher density and higher integration have been pursued forvarious kinds of typical semiconductor devices which require microprocessing of a half micron order. This leads to an ever growing demandfor the photolithography technology to form micro circuit patterns.

[0005] One way of achieving micro patterns is to shorten the wavelengthof exposure light which is used in forming a pattern using aphotoresist. Therefore, a consideration has been given to the use of anKrF excimer laser having a shorter wavelength (=248 nm) in place of irays (wavelength=365 nm) which have been used so far as the exposurelight source in the mass production of DRAMs of 256 Mbits (processingsize of 0.25 micrometers or smaller). Further, the fabrication of DRAMshaving an integration scale of 1 Gbits (processing size of 0.18micrometers or smaller) or greater which demands a finer processingtechnique needs a light source of a shorter length. For this purpose,the use of photolithography using an ArF excimer laser (193 nm) is underconsideration.

[0006] Photolithography using an excimer laser requires an improvementon the cost performance of the laser because the service life of the gasthat is the raw material to cause laser oscillation is short and thelaser device itself is expensive. In view of the above, there areincreasing demands for higher sensitivity as well as for higherresolution which matches the microminiaturized processing size.

[0007] A chemical sensitization resist which uses a photoacid generatoras a photosensitive agent is well known as a highly-sensitivephotoresist. The feature of the chemical sensitization resist lies inthat a protonic acid produced from the photoacid generator containing inthe resist by irradiation of light causes an acid catalytic reactionwith the base resin or the like of the resist in a heat treatment afterexposure. This chemical sensitization resist has achieved an extremelyhigh sensitivity as compared with the conventional resist that has aphotoreaction efficiency (reaction per photon) of less than 1. A typicalexample of the chemical sensitization resist is a positive resistdescribed in Examined Japanese Patent Application KOKOKU Publication No.H2-27660, which consists of a combination of triphenylsulfoniumhexafluoroarsenate and poly(p-tert-butoxycarboxy-α-methylstyrene). As anegative photoresist, a resist consisting of a combination ofpolyvinylphenol and a melamine derivative disclosed in Proceeding ofSPIE, vol. 1086, pp. 34-45 (1989) by L. E. Bogan et al.

[0008] Resins having a benzene ring, such as novolak and polyvinylphenolhave been used for resists for the g rays, i rays and KrF excimer laser.But, resins having a benzene ring show a significant high lightabsorption with respect to light having a wavelength of 220 nm orshorter, such as the light from the ArF excimer laser. If those resistsare used in photolithography using the ArF excimer laser, most of theexposure light is absorbed by the surface of the thin film so that theexposure light does not reach the substrate. This disables the formationof a fine resist pattern. The resins that have been used for resists forg rays, i rays and the KrF excimer laser cannot be adapted for use inphotolithography using light with a short wavelength of 220 nm orshorter. With regard to the resists for the g rays, i rays and KrFexcimer laser, however, the dry etching resistance that is essential forresists for manufacturing semiconductors are actually acquired from thebenzene ring in each resin so that it is not good enough to simply usethe benzene ring. That is, resists for exposure with the ArF excimerlaser should have an etching resistance without containing a benzenering and be transparent with respect to the wavelength of 220 nm orshorter.

[0009] Active studies are being made on positive resists which have ahigh transparency to the ArF excimer laser light (193 nm) and have a dryetching resistance. Resins having an alicyclic hydrocarbon group areused as the base resin in those resists. Typical examples include acopolymer having a unit of adamantylmethacrylate (Journal ofPhotopolymer Science and Technology, vol. 5 (no. 3), pp. 439-446 (1992)by Takechi et al.), a copolymer consisting of adamantylmethacrylate andoxocyclomethacrylate (Journal of Photopolymer Science and Technology,vol. 7, p. 31 (1994) by Takahashi et al.), a copolymer having a unit ofisobornylmethacrylate (Journal of Photopolymer Science and Technology,vol. 8 (no. 4), pp. 623-636 (1995) and vol. 9 (no. 3), pp. 465-474(1996) by R. D. Allen et al.), and a copolymer having a unit ofcarboxylated tricyclodecyl-methylmethacrylate (Proceeding of SPIE, vol.2724, pp. 377-385 (1996).

[0010] On the other hand, very few studies have been made on negativephotoresists for exposure by the ArF excimer laser. The only negativephotoresist that provides a high resolution is the negative photoresistconsisting of a combination ofpoly(carboxytetracyclododecylacrylate-hydroxytricyclodecylacrylate),tetrakis(methoxymethyl)glycoluril and tri phenyls ulfoniumtriflateproposed by the present inventors. Proceeding of SPIE, vol. 3333, pp.417-424 (1998) describes this resist having a resolution of 0.18micrometers.

[0011] In resins which use alicyclic (meth)acrylate having a hydroxylgroup like hydroxytricyclodecylacrylate, the hydroxyl group has both aneffect of improving the adhesion to the substrate and a reactivity to acrosslinking agent like tetrakis(methoxymethyl)glycoluril. Therefore,alicyclic (meth)acrylate having a hydroxyl group can be used as the baseresin for a negative photoresist without copolymerization of norborneneand maleic anhydride disclosed in Unexamined Japanese Patent ApplicationKOKAI Publication No. H10-10739.

[0012] Hydroxytricyclo[5.2.10^(2,6)[decyl(meth)acrylate disclosed inJapanese Patent No. 2776273, and tricyclodecandimethanolmonoacrylatedisclosed in Unexamined Japanese Patent Application KOKAI PublicationNo. H10-307400 are known as alicyclic (meth)acrylate having a hydroxylgroup.

[0013] If such negative photoresists have an insufficient crosslinkingdensity, they are apt to be swelled in a developer, resulting in patterndeformation, or stripping of the obtained patterns is likely to occurdue to insufficient adhesion.

SUMMARY OF THE INVENTION

[0014] Accordingly, it is an object of the present invention to providea negative photoresist which is suitable for use in photolithographyusing light of 220 nm or shorter like the light from the ArF excimerlaser as exposure light, avoids pattern deformation originated fromswelling and has a high adhesion strength to the substrate (a micropattern is hard to be stripped from the substrate) in addition to a dryetching resistance and high resolution.

[0015] To achieve the above object, the present inventors have madeextensive studies and found that the object could be achieved by amonomer having a diol structure, a polymer thereof, a negativephotoresist composition and a pattern forming method using the same.

[0016] A monomer according to the first aspect of this invention has adiol structure represented by a following formula (1):

[0017] where R¹ is a hydrogen atom or methyl group, R² is a C₂-C₆alkylene group and X is an alicyclic alkyl group having a diolstructure.

[0018] X in the formula (1) is an alicyclic alkyl group having a diolstructure represented by a following formula (2), (3), (4) or (5):

[0019] where n is an integer from 0 to 3, R³ and R⁴ are a hydrogen atomor methyl group,

[0020] where R⁵ is a hydrogen atom or methyl group,

[0021] where R⁶ is a hydrogen atom or methyl group, or

[0022] where R⁷ is a hydrogen atom or methyl group.

[0023] A polymer according to the second aspect of this invention has adiol structure having a repeating unit represented by a followingformula (6):

[0024] where R¹ is a hydrogen atom or methyl group, R² is a C₂-C₆alkylene group and X is an alicyclic alkyl group having a diolstructure.

[0025] X in the formula (6) is an alicyclic alkyl group having a diolstructure represented by a following formula (7), (8), (9) or (10):

[0026] where n is an integer from 0 to 3, R³ and R⁴ are a hydrogen atomor methyl group,

[0027] where R⁵ is a hydrogen atom or methyl group,

[0028] where R⁶ is a hydrogen atom or methyl group, or

[0029] where R⁷ is a hydrogen atom or methyl group.

[0030] It is desirable that the polymer has a diol structure representedby a following formula (11) and a weight average molecular weight of1,000 to 50,000:

[0031] where R¹ and R²are the same as those in the formula (6), X is thesame as that in any of the formulae (6) to (170), R⁸ is a hydrogen atomor methyl group, is a C₇-C₁₈ crosslinked cyclic hydrocarbon group havinga carboxyl group, R¹⁰ is a hydrogen atom or methyl group, R¹¹ is aC₇-C₁₃ hydrocarbon group having a hydroxyl group, R¹² is a hydrogen atomor methyl group, R¹³ is a hydrogen atom or a C₁-C₁₂ hydrocarbon grouphaving a hydroxyl group, and w, x, y and z are arbitrary valuessatisfying w+x+y+z=1, 0<w≦1, 0≦x<1, 0≦y<1 and 0≦z<1.

[0032] A negative photoresist composition according to the third aspectof this invention contains a polymer having a diol structure accordingto the second aspect of this invention, a crosslinking agent comprisedof a compound containing a functional group represented by a followingformula (12) and a photoacid generator which generates acid by exposure:

[0033] where R¹⁴ is a hydrogen atom, a C₁-C₆ alkyl group or a C₃-C₆oxoalkyl group.

[0034] The negative photo resist composition may further contain apolyhydric alcohol compound.

[0035] The crosslinking agent may be comprised of at least one ofcompounds represented by following formulae (13) to (17):

[0036] where R¹⁴ is the same as that in the formula (12), a₁ is 1 or 2,a₂ is 1 or 2, b₁ is 0 or 1, b₂ is 0 or 1, a₁+b₁=2 and a₂+b₂=2,

[0037] where R¹⁴ is the same as that in the formula (12), R¹⁵ is ahydrogen atom, a hydroxyl group, a C₁-C₆ alkoxy group or a C₃-C₆oxoalkyloxy group,

[0038] where R¹⁴ is the same as that in the formula (12), R¹⁵ is ahydrogen atom, a hydroxyl group, a C₁-C₆ alkoxy group or a C₃-C₆oxoalkyloxy group, and R¹⁷ is an oxygen atom, a sulfur atom, a C₁-C₃alkylene group or a hydroxymethylene group,

[0039] where R¹⁴ is the same as that in the formula (12), R¹⁸ is ahydrogen atom or a methyl group, and

[0040] The photoacid generator may be comprised of at least one of asulfonium salt compound represented by a following formula (18), aniodonium salt compound represented by a following formula (20), an imidecompound represented by a following formula (21) and a diazo compoundrepresented by a following formula (22):

[0041] where R¹⁹, R²⁰ and R²¹ are independently an alkyl-substituted,halogen-substituted or unsubstituted aromatic group, an alicyclic alkylgroup, a crosslinked cyclic hydrocarbon group, a 2-oxoalicyclic alkylgroup or an alkyl group, Y⁻ is BF₄ ⁻, AsF₆ ⁻, SbF₆ or an ion representedby a following formula (19),

Z—SO₃ ⁻  (19)

[0042] where Z is CnF_(2n+1) (n is an integer from 1 to 6), an alkylgroup or an alkyl-substituted, halogen-substituted or unsubstitutedaromatic group,

[0043] where R²² and R²³ are independently an alkyl-substituted,halogen-substituted or unsubstituted aromatic group, an alicyclic alkylgroup, a crosslinked cyclic hydrocarbon group, a 2-oxoalicyclic alkylgroup or an alkyl group, and Y⁻ is the same as that in the formula (18),

[0044] where R²⁴ is a halogen-substituted or unsubstituted alkylenegroup, an alkyl-substituted, halogen-substituted or unsubstituteddihydric aromatic group, and R²⁵ is a halogen-substituted orunsubstituted alkyl group, an alkyl group or a halogen-substituted orunsubstituted aromatic group, and

[0045] where R²⁶ and R²⁷ are independently a halogen-substituted orunsubstituted alkyl group, a halogen-substituted or unsubstitutedaromatic group or an alicyclic hydrocarbon group.

[0046] It is desirable that the negative photoresist compositioncontains 50 to 98 parts by weight of the polymer, 1 to 50 parts byweight of the crosslinking agent and 0.2 to 15 parts by weight of thephotoacid generator.

[0047] A resist pattern forming method according to the fourth aspect ofthis invention comprises a step of applying a negative photoresistcomposition as recited in claim 7 onto a substrate to be processed; astep of exposing the negative photoresist composition with light havinga wavelength of 180 to 220 nm; a baking step; and a developing step.

[0048] ArF excimer laser light may be used as the light having awavelength of 180 to 220 nm.

BRIEF DESCRIPTION OF THE DRAWINGS

[0049]FIGS. 1A to 1D are explanatory diagrams illustrating a resistpattern forming method according to this invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0050] Preferred embodiments of the present invention will now bedescribed specifically.

[0051] 1. A Monomer Having a Diol Structure

[0052] A monomer according to this invention has a diol structurerepresented by the formula (1). In the formula (1), X is an alicyclicalkyl group having a diol structure. Examples of the alicyclic alkylgroup having a diol structure include alicyclic alkyl groupsrespectively represented by the formulae (2), (3), (4) and (5).

[0053] More specifically, they include a3,4-dihydroxytricyclo[5.2.1.0^(2,6)]decyl group,3,4-dihydroxy-dimethyltricyclo[5.2.1.0^(2,6)]decyl group,3,4-dihydroxytetracyclo[4.4.0.1^(2,5).1^(7,10)]dodecylmethyl group,3,4-dihydroxy-8-methyl-tetracyclo[4.4.0.1^(2,5).1^(7,10)] dodecylmethylgroup and dihydroxyadamantyl group, which are given in Table 1,dihydroxyisobornyl group and dihydroxyisobornyl group. TABLE 1 Xchemical structure of group 3,4-dihydroxytricyclo [5.2.1.0^(2,6)] decylgroup

3,4-dihydroxy-dimethyltricyclo [5.2.1.0^(2,6)] decyl group

3,4-dihydroxytetracyclo [4.4.0.1^(2,5).1^(7,10)]-dodecylmethyl group

3,4-dihydroxy-8-methyl-tetracyclo [4.4.0.1^(2,5).1^(7,10)]-dodecylmethylgroup

3,4-dihydroxy-8-methyl-tetracyclo [4.4.0.1^(2,5).1^(7,10)]-dodecylmethylgroup

3,4-dihydroxy-8-methyl-tetracyclo [4.4.0.1^(2,5).1^(7,10)]-dodecylmethylgroup

dihydroxyadamantyl group

[0054] A monomer according to this invention, e.g., an alicyclic(meth)acrylate derivative having a diol structure, can be synthesized asfollows. An alicyclic (meth)acrylate having an unsaturated bondrepresented by the following formula (23) is subjected to epoxidationwith a peroxide like m-chloroperbenzoic acid to yield alicyclicepoxy(meth)acrylate represented by the following formula (24), then ringopening of an epoxy group is carried out with perchloric acid, therebyyielding the alicyclic (meth)acrylate derivative.

[0055] The alicyclic (meth)acrylate used here that is represented by theformula (24) can be acquired by the reaction of alicyclic alcoholrepresented by the following formula (25) with (meth)acryloyl chlorideusing an alkaline catalyst like tertiary amine. It can also be acquiredby the reaction of alicyclic alcohol represented by the followingformula (25) with (meth)acrylate using an acidic catalyst liketrifluoroacetic acid.

[0056] where R¹ is a hydrogen atom or methyl group, R²is a C₂-C₆alkylene chain and n is an integer from 0 to 3.

[0057] where R¹ is a hydrogen atom or methyl group, R² is a C₂-C₆alkylene chain and n is an integer from 0 to 3.

[0058] where n is an integer from 0 to 3.

[0059] 2. A Polymer Having a Diol Structure

[0060] A polymer according to this invention has a diol structure havinga repeating unit represented by the formula (6).

[0061] The polymer according to this invention can be acquired bypolymerization of the aforementioned monomer using an adequate radicalpolymerization initiator.

[0062] Specifically, this polymer can be acquired by adding a radicalpolymerization initiator like azobisisobutyro-nitrile or benzoylperoxide into a solvent such as tetrahydrofuran under the inert gas(argon, nitrogen or the like) atmosphere and heating and stirring theresultant product at 50 to 70 degrees Celsius for 5 to 12 hours.

[0063] A specific example of the polymer according to this invention isa polymer which has a diol structure represented by the formula (11) anda weight average molecular weight of 1,000 to 50,000.

[0064] In the formula (11), R⁹ may specifically be acarboxytricyclo[5.2.1.0^(2,6)]decylmethyl group,carboxytricyclo[5.2.1.0^(2,6)]decyl group, carboxyadamantyl group,carboxynorbornyl group, carboxymethylnorbornyl group, carboxyisobornylgroup, carboxytetracyclo[4.4.0.1^(2,5).1^(7,10)]-dodecyl group,carboxymethyltetracyclo[4.4.0.1^(2,5).1^(7,10)]-dodecyl group, which aregiven in Table 2, or the like, but is in no way limited to those groups.

[0065] Unexposed negative photoresist should be dissolved into adeveloper to be patterned, and an alicyclic group having a carboxylgroup works to increase the dissolving speed to the developer for anegative photoresist. Crosslinked cyclic hydrocarbon works to improvethe dry etching resistance. TABLE 2 R⁹ chemical structure of groupcarboxytricyclo [5.2.1.0^(2,6)] decylmethyl group

carboxytricyclo [5.2.1.0^(2,6)] decyl group

carboxyadamantyl group

carboxynorbornyl group

carboxymethylnorbornyl group

carboxyisobornyl group

carboxytetracyclo [4.4.0.1^(2.5).1^(7,10)] dodecyl group

carboxymethyltetracyclo [4.4.0.1^(2,5).1^(7,10)] dodecyl group

[0066] R¹¹ may specifically be a hydroxyethyl group, hydroxypropylgroup, hydroxybutyl group, hydroxycyclohexyl group,hydroxydimethylcyclohexyl group, hydroxytricyclo-[5.2.1.0^(2,6)]decylgroup, hydroxyadamantyl group, hydroxynorbornyl group, hydroxyisobornylgroup, hydroxytetracyclo[4.4.0.1^(2,5).1^(7,10)]dodecyl group or thelike, but is not limited to those groups.

[0067] R¹³ may specifically be any of a methyl group, ethyl group,n-propyl group, isopropyl group, n-butyl group, isobutyl group, t-butylgroup, cyclohexyl group, dimethylcyclohexyl group,tricyclo[5.2.1.0^(2,6)]decyl group, adamantyl group, norbornyl group,isobornyl group, tetracyclo(4.4.0.1^(2,5).1^(7,10)]dodecyl group or thelike, but is not limited to those groups.

[0068] The polymer represented by the formula (11) can be obtained bypolymerization of a monomer using a proper radical polymerizationinitiator. Specifically, this polymer can be acquired by adding aradical polymerization initiator like azobisisobutyronitrile or benzoylperoxide into a solvent such as tetrahydrofuran under the inert gas(argon, nitrogen or the like) atmosphere and heating and stirring theresultant product at 50 to 70 degrees Celsius for 5 to 12 hours. Apolymer having an arbitrary copolymerization ratio by selecting thepolymerization conditions such as the content ratio of the monomer. Theweight average molecular weight of this polymer is preferably 1,000 to500,000, and is more preferably 3,000 to 200,000. A polymer with aweight average molecular weight of less than 1,000 has a low glasstransition point and may become hard to be treated as a resist, while apolymer with a weight average molecular weight of over 500,000 may havea difficulty in providing a uniform film on the substrate.

[0069] 3. Negative Photoresist Composition

[0070] A negative photoresist composition according to this inventioncontains the aforementioned polymer, a crosslinking agent, a photoacidgenerator and, as needed, a polyhydric alcohol compound.

[0071] A possible crosslinking agent is a compound containing a grouprepresented by the formula (12). A compound containing a functionalgroup represented by the formula (12) has such a property as to bereacted with a hydroxyl group in the manner shown by the followingreaction formula (A) under the presence of an acidic catalyst. That is,a polymer having a hydroxyl group is crosslinked with a compoundcontaining a functional group represented by the formula (12) under thepresence of an acidic catalyst. If this polymer is dissolvable in adeveloper, this crosslinking makes the polymer undissolvable in adeveloper.

[0072] The negative photoresist composition according to this inventioncontains a polymer having an alicyclic alkyl group with a diol structurehaving two hydroxyl groups in a repeating unit. That is, the polymer inthe negative photoresist according to this invention has many reactionpoints to a crosslinking agent as compared with known polymers having amonool.

[0073] Further, an alicyclic alkyl hydroxide group (X in the generalformula (6)) in the polymer in the negative photoresist of thisinvention has an alkylene chain (R² in the general formula (6)) betweenthe alicyclic alkyl group and the principal chain of the polymer, thedegree of freedom of the resist film is relatively large. This enhancesthe reactivity to a crosslinking agent. In other words, since thepolymer in the negative photoresist according to this invention has manyreaction points to a crosslinking agent and a high reactivity to acrosslinking agent, it can provide a high crosslinking density.

[0074] When a polymer containing a group having a diol structure is usedin a negative photoresist, pattern deformation originated frominsufficient crosslinking is hard to occur. As a polymer containing agroup having a diol structure has two polar groups which work to improvethe adhesion to the substrate, the resist pattern formed will not beseparated easily from the substrate.

[0075] where R¹⁴ is a hydrogen atom, a C₁-C₆ alkyl group or a C₃-C₆oxoalkyl group.

[0076] Compounds containing a group represented by the formula (26) mayinclude compounds represented by a formula (17) and the followingformula (28).

[0077] where R¹⁴ is a hydrogen atom, a C₁-C₆ alkyl group (whichspecifically is a methyl group, ethyl group, propyl group, isopropylgroup, butyl group, isobutyl group, tertiary butyl group, pentyl group,hexyl group or the like, but is not limited to those groups) or a C₃-C₆oxoalkyl group (which specifically is a β-oxopropyl group, β-oxobutylgroup, β-oxoheptyl group, β-oxohexyl group or the like, but is notlimited to those groups), a₁ is 1 or 2, a₂ is 1 or 2, b₁ is 0 or 1, b₂is 0 or 1, a₁+b₁=2 and a₂+b₂=2.

[0078] where R¹⁴ is the same as that in the formula (28), R¹⁵ is ahydrogen atom, a hydroxyl group, a C₁-C₆ alkoxy group (whichspecifically is a methoxy group, ethoxy group, propoxy group, isopropoxygroup, butoxy group, isobutoxy group, tertiary butoxy group, pentyloxygroup, hexyloxy group or the like, but is not limited to those groups)or a C₃-C₆ oxoalkyloxy group (which specifically is β-oxopropoxy group,β-oxobutoxy group, β-oxoheptyloxy group, β-oxohexyloxy group or thelike, but is not limited to those groups).

[0079] where R¹⁴ is the same as that in the formula (28) and R¹⁷ is anoxygen atom, a sulfur atom, a C₁-C₃ alkylene group (which specificallyis a methylene group, ethylene group, propylene group, 1-methylethylenegroup or the like, but is not limited to those groups) or ahydroxymethylene group,

[0080] where R¹⁴ is the same as that in the formula (28), R¹⁸ is ahydrogen atom, a methyl group or an ethyl group.

[0081] In the compounds containing a group shown by the formula (26)which is a crosslinking agent in the negative photoresist composition ofthe invention, methylolurea in which R¹⁴ is a hydrogen atom, forexample, can be synthesized by methylolation of urea with formaldehyde.

[0082] The compounds represented by the formula (28) where R¹⁴ is analkyl group or oxoalkyl group can be obtained by processing methylolureawith the corresponding alcohol. For example, processing methylolureawith methanol can yield dimethylated methylolurea [in the formula (28),R¹⁴ is a methyl group (C, alkyl group)], processing it with ethanol canyield diethylated methylolurea [in the formula (28), R¹⁴ is an ethylgroup (C₂ alkyl group)], processing it with isobutanol can yielddiisobutylated methylolurea [in the formula (28), R¹⁴ is an isobutylgroup (C₄ alkyl group)], and processing it with 2-oxopropanol (alsocalled “hydroxyacetone”) can yield di-β-oxopropylated methylolurea [inthe formula (28), R¹⁴ is a β-oxopropyl group (C₃ oxoalkyl group)].

[0083] In the compounds represented by the formula (29), for example,1,3-bis(hydroxymethyl)ethyleneurea (also called“1,3-dimethylolimidazolidone-2”) in which R¹⁴ in the formula (29) is ahydrogen atom and R¹⁵ is a hydrogen atom can be obtained by the reactionof urea with ethylenediamine and formaldehyde.

[0084] The compounds represented by the formula (29) where R¹⁴ is analkyl group or oxoalkyl group and R¹⁵ is a hydrogen atom can be obtainedby processing 1,3-bis(hydroxymethyl)-ethyleneurea with the correspondingalcohol. For example, processing 1,3-bis(hydroxymethyl)ethyleneurea withmethanol can yield 1,3-bis(methoxymethyl)ethyleneurea [in the formula(29), R¹⁴ is a methyl group (C₁ alkyl group) and R¹⁵ is a hydrogenatom], processing it with ethanol can yield1,3-bis(ethoxymethyl)ethyleneurea [in the formula (29), R¹⁴ is an ethylgroup (C₂ alkyl group) and R¹⁵ is a hydrogen atom], processing it withisobutanol can yield 1,3-bis-(isobutoxymethyl)ethyleneurea [in theformula (29), R¹⁴ is an isobutyl group (C₄ alkyl group) and R¹⁵ is ahydrogen atom], and processing it with 2-oxopropanol (also called“hydroxyacetone”) can yield 1,3-bis(β-oxopropoxymethyl)ethyleneurea [inthe formula (29), R¹⁴ is a 2-oxopropyl group (C₃ oxoalkyl group) and R¹⁵is a hydrogen atom].

[0085] 1,3-bis(hydroxym ethyl)-4,5-bis (hydroxy)ethyleneurea (alsocalled “1,3-dimethylol-4,5-dihydroxyimidazolidone-2”) in which R¹⁴ inthe formula (29) is a hydrogen atom and R¹⁵ is a hydroxyl group can beobtained by the reaction of urea with glyoxal and then by performingmethylolation using formaldehyde.

[0086] The compounds in the formula (29) where R¹⁴ is an alkyl group oroxoalkyl group and R¹⁵ is an alkoxy group or oxoalkoxy group can beobtained by processing1,3-bis(hydroxymethyl)-4,5-bis(hydroxy)ethyleneurea with the associatedalcohol. For example, processing1,3-bis-(hydroxymethyl)-4,5-bis(hydroxy)ethyleneurea with methanol canyield 1,3-bis(methoxymethyl)-4,5-bis(methoxy)-ethyleneurea [in theformula (29), R¹⁴ is a methyl group (C₁ alkyl group) and R¹⁵ is amethoxy group (C₁ alkoxy group)], processing it with ethanol can yield1,3-bis-(ethoxymethyl)-4,5-bis(ethoxy)ethyleneurea [in the formula (29),R¹⁴ is an ethyl group (C₂ alkyl group) and R¹⁵ is an ethoxy group (C₂alkoxy group)], processing it with isopropanol can yield1,3-bis(isopropoxymethyl)-4,5-bis(isopropoxy)ethyleneurea [in theformula (29), R¹⁴ is an isopropyl group (C₃ alkyl group) and R¹⁵ is apropyloxy group (C₃ alkoxy group)], processing it with tertiary butanolcan yield 1,3-bis(tertiary butoxymethyl)-4,5-bis(tertiarybutoxy)ethyleneurea [in the formula (29), R¹⁴ is a tertiary butyl group(C₄ alkyl group) and R¹⁵ is a tertiary butoxy group (C₄ alkoxy group)],and processing it with 2-oxopropanol (also called “hydroxyacetone”) canyield 1,3-bis(β-oxopropoxymethyl)-4,5-bis(β-oxopropoxy)-ethyleneurea [inthe formula (29), R¹⁴ is a β-oxopropyl group (C₃ oxoalkyl group) and R¹⁵is a β-oxopropyroxy group (C₃ oxoalkoxy group)].

[0087] In the compounds represented by the formula (30), for example,1,3-bis(hydroxymethyl)-tetrahydro-2(1H)-pyrimidinone where R¹⁴ and RIBin the formula (30) are hydrogen atoms and R¹⁷ is a methylene group canbe obtained by the reaction of urea with propyrenediamine and then thereaction of the resultant product with formaldehyde.

[0088] When R¹⁴ is an alkyl group, R¹⁶ is a hydrogen atom and R¹⁷ is amethylene group in the formula (30), the compound can be obtained byprocessing 1,3-bis(hydroxymethyl)-tetrahydro-2(1H)pyrimidinone with thecorresponding alcohol. For example, processing1,3-bis(hydroxymethyl)-tetrahydro-2(1H)pyrimidinone with methanol canyield dimethylated 1,3-bis(hydroxymethyl)-tetrahydro-2(1H)pyrimidinone[in the formula (30), R¹⁴ is a methyl group (C₂ alkyl group), R¹⁶ is ahydrogen atom and R¹⁷ is a methylene group (C₁ alkylene group)],processing it with ethanol can yield diethylated1,3-bis(hydroxymethyl)-tetrahydro-2(1H)pyrimidinone [in the formula(30), R¹⁴ is an ethyl group (C₂ alkyl group), R¹⁶ is a hydrogen atom andR¹⁷ is a methylene group (C₁ alkylene group)], and processing it withisobutanol can yield butylated1,3-bis(hydroxymethyl)tetrahydro-2(1H)pyrimidinone [in the formula (30),R¹⁴ is an isobutyl group (C₄ alkyl group), R¹⁶ is a hydrogen atom andR¹⁷ is a methylene group (C₁ alkylene group)].

[0089] Dimethyloluron represented by the formula (30) where R¹⁴ and R¹⁶is a hydrogen atom and R¹⁷ is an oxygen atom can be acquired by thereaction of urea with formaldehyde whose molecular amount is four timesthat of urea.

[0090] 1,3-bis(hydroxymethyl)-tetrahydro-5-hydroxy-2(H)pyrimidinonewhere R¹⁴ and R¹⁶ are hydrogen atoms and R¹⁷ is a hydroxymethylene groupcan be obtained by the reaction of urea with 2-hydroxypropyrenediamineand then the reaction of the resultant product with formaldehyde.

[0091] In the case of the compounds represented by the formula (31), forexample, 1,3,4,6-tetrakis-(hydroxymethyl)glycoluril (also called“1,3,4,6-tetrakis(hydroxym ethyl)acetyleneurea, tetramethylolatedglyoxazolediurein) in which R¹⁴ in the general formula (31) is ahydrogen atom and R¹⁸ is a hydrogen atom can be obtained by the reactionof glyoxazole with urea whose molecular amount is twice that ofglyoxazole and then by performing methylolation using formaldehyde.

[0092] The compounds in the formula (31) where R¹⁴ is an alkyl group oroxoalkyl group and R¹⁸ is a hydrogen atom can be obtained by processing1,3,4,6-tetrakis(hydroxymethyl)-glycoluril with the associated alcohol.For example, processing 1,3,4,6-tetrakis(hydroxymethyl)glycoluril withmethanol can yield 1,3,4,6-tetrakis(methoxymethyl)glycoluril (in theformula (31), R¹⁴ is a methyl group (C₁ alkyl group) and R¹⁸ is ahydrogen atom], processing it with ethanol can yield1,3,4,6-tetrakis(ethoxymethyl)glycoluril [in the formula (31), R¹⁴ is anethyl group (C₂ alkyl group) and R¹⁸ is a hydrogen atom], processing itwith isobutanol can yield 1,3,4,6-tetrakis(isobutoxymethyl)glycoluril[in the formula (31), R¹⁴ is an isobutyl group (C₄ alkyl group) and R¹⁸is a hydrogen atom], and processing it with 2-oxopropanol (also called“hydroxyacetone”) can yield1,3,4,6-tetrakis(β-oxopropoxymethyl)glycoluril [in the formula (30), R¹⁴is a β-oxopropyl group (C₃ oxoalkyl group) and R¹⁸ is a hydrogen atom].

[0093] A preferable photoacid generator used in this invention shouldgenerate acid by irradiation of light of 180 nm to 220 nm and should besuch that the mixture of this photoacid generator and the polymer in theabove-described resist composition of the invention is dissolvedsufficiently in an organic solvent and a film forming method like spincoating using this solution can form a uniform film coat. Further, asingle photoacid generator may be used alone or in combination with oneor more kinds of photoacid generators.

[0094] Some examples of usable photoacid generators are a sulfonium saltcompound represented by the following formula (32), an iodonium saltcompound represented by the following general formula (34), asuccinimide derivative represented by the following general formula(35), a diazo compound represented by the following general formula(36), a 2,6-dinitrobenzyl ester group and a disulfon compound.

[0095] Their specific examples include a triphenyisulfonium saltderivative disclosed in Journal of the Organic Chemistry, vol. 43, no.15, pp. 3055-3058 (1978) by J. V. Crivello et al., a diphenyliodoniumsalt derivative disclosed in Journal of the Polymer Science, vol. 56,pp. 383-395 (1976) by J. V. Crivello et aL., an alkylsulfonium saltderivative such as cyclohexylmethyl(2-oxocyclohexyl)sulformiumtrifluoromethanesulfonate disclosed in Unexamined Japanese PatentApplication KOKAI Publication No. H7-28237, and a sulfonium saltcompound having a crosslinked cyclic alkyl group such asβ-oxocyclohexylmethyl(2-norbornyl)sulformium trifluoromethanesulfonatedisclosed in Unexamined Japanese Patent Application KOKAI PublicationNo. H8-27102. Other examples include a succinimide derivative such asester N-hydroxy-succinimidemethanesulfonate disclosed in UnexaminedJapanese Patent Application KOKAI Publication Nos. H6-214391, H7-181678and H7-295220, a 2,6-dinitrobenzyl ester group [Proceeding of SPIE, vol.1262, p. 32 (1990) by O. Nalamasu et al.],1,2,3-tri(methanesulfonyloxy)benzene [Proceeding of PME '89 By TakumiUeno et al., Kodansya, pp. 413-424 (1990)] and a disulfon compound.

[0096] where R¹⁹, R²⁰ and R²¹ are independently an alkyl-substituted,halogen-substituted or unsubstituted aromatic group, an alicyclic alkylgroup, a crosslinked cyclic hydrocarbon group, a 2-oxoalicyclic alkylgroup or an alkyl group, Y⁻ is BF₄ ⁻, AsF₆ ⁻, SbF₆ or an ion representedby the following formula (33),

Z—SO₃ ⁻  (33)

[0097] where Z is C_(n)F_(2n+1) (n is an integer from 1 to 6), an alkylgroup or an alkyl-substituted, halogen-substituted or unsubstitutedaromatic group,

[0098] where R²² and R²³ are independently an alkyl-substituted,halogen-substituted or unsubstituted aromatic group, an alicyclic alkylgroup, a crosslinked cyclic hydrocarbon group, a 2-oxoalicyclic alkylgroup or an alkyl group, and Y⁻ is the same as that in the formula (32),

[0099] where R²⁴ is a halogen-substituted or unsubstituted alkylenegroup, an alkyl-substituted, halogen-substituted or unsubstituteddihydric aromatic group, and R²⁵ is a halogen-substituted orunsubstituted alkyl group, an alkyl group or a halogen-substituted orunsubstituted aromatic group, and

[0100] where R²⁶ and R²⁷ are independently a halogen-substituted orunsubstituted alkyl group, a halogen-substituted or unsubstitutedaromatic group or an alicyclic hydrocarbon group.

[0101] When polyhydric alcohol (dihydric alcohol or more valencesalcohol) is contained in the negative photoresist composition of thisinvention, the resolution is improved in some cases. This is becausepolyhydric alcohol which has a high reactivity to a crosslinking agentworks as a crosslinking promotor.

[0102] Examples of polyhydric alcohol used as needed in this inventioninclude ethylene glycol, glycerol, 1,2-butanediol, 1,3-butanediol,1,4-butanediol, 2,3-butanediol, 1,2,4-butanetriol, 1,2-pentanediol,1,4-pentanediol, 1,5-pentanediol, 2,4-pentanediol, 1,2-hexanediol,1,5-hexanediol, 1,6-hexanediol, 2,5-hexanediol, 1,2-cyclohexanediol,1,3-cyclohexanediol, 1,4-cyclohexanediol, 1,2-cyclohexanedim ethanol, 1,4-cyclohexanedimethanol, 1,3,5-cyclohexanetrimethanol,1,2-cyclopentanediol, 1,3-cyclopentanediol, 1,2-cyclooctanediol,1,5-cyclooctanediol, tricyclodecandimethanol, 2,3-norbornanediol,2(3)-hydroxy-5,6-bis(hydroxymethyl)norbornane,2,3-dihydroxy-5(6)hydroxymethylnorbornane, 1,4-anhydroerythriol,L-arabinose, L-arabitol, D-cellobiose, cellulose, 1,5-decalindiol,glucose, galactose, lactose, maltose, mannose and mannitol, though theyare in no way restrictive.

[0103] The ratio of the content of the polymer having a diol structurein the negative photoresist composition of this invention is normally 50to 98 parts by weight with respect to 100 parts by weight of the entirestructural components including itself, and is preferably 70 to 95 partsby weight. When the ratio of this content is less than 50 parts byweight, it is difficult to form a uniform film. When the ratio of thiscontent exceeds 98 parts by weight, the amounts of the crosslinkingagent and photoacid generator to be introduced inevitably becomesmaller. This results in insufficient crosslinking, thus disablingpattern acquisition.

[0104] The ratio of the content of the crosslinking agent is normally 1to 50 parts by weight with respect to 100 parts by weight of the entirestructural components including itself, and is preferably 10 to 30 partsby weight. When the ratio of this content is less than 1 part by weight,sufficient crosslinking of the polymer does not occur, thus disablingpattern acquisition. When the ratio of this content exceeds 50 parts byweight, it is difficult to form a uniform film and the transparency ofthe thin film may lower. Further, the ratio of the polymer content isinsufficient so that a sufficient etching resistance may not beobtained.

[0105] The ratio of the content of the photoacid generator is normally0.2 to 15 parts by weight with respect to 100 parts by weight of theentire structural components including itself, and is preferably 0.5 to10 parts by weight. When the ratio of this content is less than 0.2 partby weight, the sensitivity of the negative photoresist composition ofthis invention lowers significantly, making it difficult to form apattern. When the ratio of this content exceeds 15 parts by weight, itbecomes difficult to form a uniform film coat and the residual (scum) islikely to be produced after development.

[0106] In a case where polyhydric alcohol is contained in the negativephotoresist composition, the amount of its content of 0.2 to 20 parts byweight with respect to 100 parts by weight of the entire structuralcomponents including itself is effective in improving the resolution.

[0107] There is no particular restriction on a solvent to be used inthis invention as long as it is an organic solvent in which the negativephotoresist composition is sufficiently dissolved and whose solution canprovide a uniform film coat using a film forming method like spincoating. If the above conditions are satisfied, any kind of solvent canbe used. Also, a single kind of solvent or more than 2kind of solventmay be used.

[0108] Specific examples of the solvent are n-propyl alcohol, isopropylalcohol, n-butyl alcohol, tert-butyl alcohol, methyl cellsolve acetate,ethyl cellsolve acetate, propylene glycol monoethyl etheracetate(1-methoxy-2-acetoxypropane), methyl lactate, ethyl lactate,2-methoxybutyl acetate, 2-ethoxyethyl acetate, methyl pyruvate, ethylpyruvate, methyl 3-methoxypropionate, ethyl 3-methoxypropioriate,N-methyl-2-pyrolidinone, cyclohexanone, cyclopentanone, cyclohexanol,methyl ethyl ketone, 1,4-dioxane, ethylene glycol monomethyl ether,ethylene glycol monomethyl ether acetate, ethylene glycol monoethylether, ethylene glycol monoisopropyl ether, diethylene glycol monomethylether, and diethylene glycol dimethyl ether, which are not howeverrestrictive.

[0109] Another components such as surfactant, coloring matter,stabilizer, coating-property modifier or die may be added to thephotoresist composition of this invention as needed.

[0110] The negative photoresist composition of this invention has, asthe base resin, a polymer having an alicyclic alkyl group which is knownto provide a high dry etching resistance. Since this polymer does nothave a benzene ring, it has a high transparency to light of a shortwavelength of 220 nm or shorter like the ArF excimer laser light.

[0111] As apparent from the above, the photoresist composition of thisinvention is a chemical sensitization type resist and has both a hightransparency to light of a short wavelength of 220 nm or shorter likethe ArF excimer laser light and a high dry etching resistance. Thisphotoresist composition can therefore be used as a new negativephotoresist material for use in fabrication of semiconductor devices.

[0112] 4. Pattern Forming Method

[0113] This invention also provides a method of forming a negativepattern of a photoresist on a substrate to be processed by using theabove-described negative photoresist composition.

[0114] First, as shown in FIG. 1A, the negative photoresist material ofthis invention is applied on a substrate 1 to be processed, thenpre-baking is performed at 60 to 170 degrees Celsius for 30 to 240seconds using heating means like a hot plate, thereby forming a resistfilm 2. Then, the resist film 2 is selectively exposed by an exposuresystem using a photomask 3, as shown in FIG. 1B. After exposure, theresist film 2 is heated. Consequently, crosslinking of the resin occursin an exposure area 4, as shown in FIG. 1C. Finally, the unexposedportion of the resist film 2 is selectively dissolved and removed by analkaline developer like a tetramethylammoniumhydroxide (TMAH) solution,thereby forming a negative pattern as shown in FIG. 1D.

EXAMPLES

[0115] Examples of this invention will now be discussed, but it is to benoted that those examples are to be considered as illustrative and in noway restrictive.

Example 1

[0116] Synthesis of 3,4-dihydroxytricyclo[5.2.1.0^(2,6)]-decyloxyethylacrylate

[0117] 39.25 g of m-chloroperbenzoic acid was placed in a 500-ml threeneck flask with a drying tube and was dissolved in 300 ml of chloroform,and the resultant solution was cooled in an ice bath. Then, 25 g (0.122mol) of dicyclopentenyloxyethyl acrylate (FA-512A manufactured byHitachi Chemical Co., Ltd.) was dropped in the liquid. After dropping,the resultant liquid was stirred for one hour under the ice coldenvironment and two hours at the room temperature. The precipitatedm-chloroperbenzoic acid was filtered out, and the filtered liquid wascleaned in 300 ml of 10% sodium hydrogensulfite solution, 200 ml of 5%sodium carbonate solution and saturated salt solution in order. Thesolution was dried with magnesium sulfate, after which chloroform wasleft under reduced pressure. As a result, the double bond of thealicyclic group of dicyclopentenyloxyethyl acrylate was epoxidated,yielding 25 g of 3,4-epoxytricyclodecyloxyethyl acrylate (93% yield).

[0118] Then, 11 g (0.05 mol) of 3,4-epoxytricyclodecyloxy-ethyl acrylatewas dissolved in 80 ml of tetrahydrofuran and iced. Then, 40 ml of a 35%perchloric acid solution was dropped in the liquid and was thereafterstirred for two hours at the room temperature. 200 ml ether was added tothe reaction solution and was cleaned with 2% sodium hydroxide until theliquid layer became alkaline. Then, the resultant solution was cleanedwith saturated salt solution after which the organic layer was driedwith magnesium sulfate. The solvent was left under reduced pressure, andthe residual was cleaned with 100 ml of hexane: acetate-ethyl blendedsolvent (5:1). Consequently, the epoxy group of3,4-epoxytricyclodecyloxyethyl acrylate was ring-opened, yielding 5 g of3,4-dihydroxytricyclodecyloxyethyl acrylate (viscous liquid, 67% yield).

[0119]¹H-NMR (CDCl₃): δ0.85-2.50 (10OH, m), 3.28-3.70 (7H, br), 4.2-4.35(2H, m), 5.8 (1H, dd), 6.15 (1H, dd), 6.43 (1H, d); IR (cm⁻¹): 3400(νOH), 2848, 2940 (νCH), 1720 (νC═O), 1618, 1625 (νC═C).

Example 2

[0120] Synthesis of 3,4-dihydroxytricyclo[5.2.1.0^(2,6)]-decyloxyethylmethacrylate

[0121] By using 30 g (0.115 mol) of dicyclopentenyloxyethyl methacrylate(a compound acquired in a synthesis example 1 to be discussed later) inplace of dicyclopentenyloxyethyl acrylate and 34 g of m-chloroperbenzoicacid, the epoxidation reaction of dicyclopentenyloxyethyl methacrylatewas carried out in the same way as used in the example 1. This yielded30.2 g of 3,4-epoxytricyclo-decyloxyethyl methacrylate (95% yield).

[0122] Then, the ring opening reaction of the epoxy group was performedby using 40 ml of a 35% perchloric acid solution in the same way as donein the example 1 using 13.5 g (0.05 mol) of3,4-epoxytricyclodecyloxyethyl methacrylate. This yielded 9.1 g of3,4-dihydroxytricyclodecyl methacrylate (viscous liquid, 63% yield).

[0123]¹H-NMR (CDCl₃): δ0.84-2.50 (12H, m), 3.28-3.70 (7H, br), 4.22-4.36(2H, m), 5.58 (1H, dd), 6.14 (1H, dd); IR (cm⁻¹): 3400 (νOH), 2848, 2940(νCH), 1720 (νC═O), 1618, 1625 (νC═C).

Example 3

[0124] Synthesis of 3,4-dihydroxytricyclo[5.2.1.0^(2,6)]-decyloxypropylmethacrylate

[0125] By using 30 g (0.11 mol) of dicyclopentenyloxypropyl acrylate inplace of dicyclopentenyloxyethyl acrylate and 34 g of m-chloroperbenzoicacid, the epoxidation reaction of dicyclopentenyloxypropyl methacrylatewas carried out in the same way as done in the example 1. This yielded30.3 g of 3,4-epoxytricyclodecyloxypropyl acrylate (96% yield).

[0126] Then, the ring opening reaction of the epoxy group was performedby using 56 ml of a 35% perchloric acid solution in the same way as donein the example 1 using 20 g (0.069 mol) of3,4-epoxytricyclodecyloxypropyl acrylate. This yielded 9.7 g of3,4-dihydroxytricyclodecyloxypropyl acrylate (viscous liquid, 46%yield).

[0127]¹H-NMR (CDCl₃): δ0.85-2.49 (12H, m), 3.28-3.70 (7H, br), 4.2-4.35(2H, m), 5.81 (1H, dd), 6.15 (1H, dd), 6.43 (1H, d); IR (cm⁻¹): 3400(νOH), 2848, 2940 (νCH), 1720 (νC═O), 1617, 1625 (νC═C).

Example 4

[0128] Synthesis of 3,4-dihydroxytricyclo[5.2.1.0^(2,6)]-decyloxybutylacrylate

[0129] By using 30 g (0.108 mol) of dicyclopentenyloxybutyl acrylate inplace of dicyclopentenyloxyethyl acrylate and 32 g of m-chloroperbenzoicacid, the epoxidation reaction of dicyclopentenyloxybutyl acrylate wascarried out in the same way as done in the example 1. This yielded 29 gof 3,4-epoxytricyclodecyloxybutyl acrylate (92.7% yield).

[0130] Then, the ring opening reaction of the epoxy group was performedby using 40 ml of a 35% perchloric acid solution in the same way as donein the example 1 using 14.6 g (0.05 mol) of3,4-epoxytricyclodecyloxybutyl acrylate. This yielded 9.52 g of3,4-dihydroxytricyclodecyloxybutyl acrylate (viscous liquid, 61.2%yield).

[0131]¹H-NMR (CDCl₃): δ0.85-2.49 (14H, m), 3.28-3.70 (7H, br), 4.2-4.35(2H, m), 5.81 (1H, dd), 6.15 (1H, dd), 6.43 (1H, d); IR (cm⁻¹): 3400(νOH), 2848, 2943 (νCH), 1720 (νC═O), 1617, 1625 (νC═C).

Example 5

[0132] Synthesis of dihydroxypentacyclo-[6.5.1.1^(3,6).0^(2,7),0^(9,13)]pentadecyloxyethyl methacrylate

[0133] By using 10 g (0.03 mol) ofpentacyclo-[6.5.1.1^(3,6).0^(2,7),0^(9,13)]pentadecyloxyethylmethacrylatein in place of dicyclopentenyloxyethyl acrylate and 10 g ofm-chloroperbenzoic acid, the epoxidation reaction was carried out in thesame way as used in the example 1. This yielded 8.9 g ofepoxypentacyclo[6.5.1.1^(3,6).0^(2,7),0^(9,13)]pentadecyl-oxyethylmethacrylate (88% yield).

[0134] Then, the ring opening reaction of the epoxy group was performedby using 40 ml of a 35% perchloric acid solution in the same way as donein the example 1 using 8 g (0.05 mol) ofepoxypentacyclo[6.5.1.1^(3,6).0^(2,7),0^(9,13)]pentadecyl-oxyethylmethacrylate. This yielded 4.9 g of3,4-dihydroxypentacyclo[6.5.1.1^(3,6).0^(2,7),0^(9,13)]pentadecyloxyethylmethacrylate (viscous liquid, 58% yield).

[0135]¹H-NMR (CDCl₃): δ0.84-2.50 (12H, m), 3.28-3.70 (7H, br), 4.22-4.36(2H, m), 5.58 (1H, dd), 6.14 (1H, dd); IR (cm⁻¹): 3400 (νOH), 2848, 2940(νCH), 1720 (νC═O), 1618, 1625 (νC═C).

Synthesis Example 1

[0136] Synthesis of dicyclopentenyloxyethyl methacrylate

[0137] 25 g (0.128 mol) of a product acquired by adding ethylene glycolto dicyclopentenyloxyethanol (dicyclopentadien) in a 500-ml three neckflask using sulfuric acid as a solvent was dissolved in 200 mltetrahydofuran and the resultant product was cooled in an ice bath.Then, 17.1 g of N, N-dimethylaniline was added to the product in which14.8 g of methacrylate chloride was further dropped. The resultantproduct was sequentially cleaned with a sodium hydroxide solution,hydrochloric acid solution and saturated salt solution, and was thensubjected to column refining with silica gel column (streaming solvent:blended solvent of hexane and ethyl acetate), thereby yieldingdicyclopentenyloxyethyl methacrylate.

Example 6

[0138] Synthesis of a polymer A1 having the following structure

[0139] 0.52 g of 3,4-dihydroxytricyclo[5.2.1.02ldecyloxy-ethyl acrylate,3.31 g of carboxytetracyclo(4.4.0.1^(2,5)1^(7,1)]-dodecyl acrylate and 5g of hydroxytricyclodecyl acrylate were dissolved in 36 ml of drytetrahydrofuran in a 100-ml flask with a reflux tube, 119 mg ofazobisisobutyronitrile (AIBN) was added there and the resultant productwas stirred at 60-65 degrees Celsius under the argon atmosphere. Aftertwo hours, the resultant product was cooled to the room temperature, 400ml hexane/ether (4/1) was poured on the reaction mixture and theprecipitate was filtered out. The resultant product was then subjectedto reprecipitation refining, yielding 4.8 g of an intended product(54.4% yield). The copolymerization ratio then was 5:33:62 as obtainedfrom the integration ratio of ¹H-NMR. The molecular weight of theacquired resin A1 was 8300; this molecular weight was measured by gelpermeation chromatography (GPC) using LC-9A manufactured by ShimadzuCorporation (column: KF-80M produced by Showa Denko K.K.) and obtainedin terms of the molecular weight of polystyrene.

Example 7

[0140] A photoresist having the following composition was prepared. Thefollowing experiment was conducted under a yellow lamp.

[0141] (a) resin A1 (the one synthesized in the example 6) 3.7 g

[0142] (b) crosslinking agent B1 (shown below) 0.28 g

[0143] (c) photoacid generator C1(triphenyisulfoniumtrifluoro-methanesulfonate; shown below) 0.02 g

[0144] (d) diethylene glycol dimethyl ether 18.2 g

[0145] The molecular weight of the resin A1 used was 8300; thismolecular weight was measured by gel permeation chromatography (GPC)using LC-9A manufactured by Shimadzu Corporation (column: KF-80Mproduced by Showa Denko K.K.) and obtained in terms of the molecularweight of polystyrene.

[0146] The above mixture was filtered with a 0.2-micrometer tetronicfilter to prepare the photoresist. This photoresist was spin-coated on a3-in. quartz substrate, and the resultant structure was then heated at120 degrees Celsius for 60 seconds on a hot plate, thus forming a thinfilm of 0.4 micrometers in thickness. The permeability of this thin filmwith respect to 193.4-nm light (the center wavelength of the ArF excimerlaser light), which was measured by an ultraviolet spectrophotometer(UV365 manufactured by Shimadzu Corporation), was 68%. This is asufficient transparency for a single-layer photoresist.

Example 8

[0147] The photoresist prepared in the example 7 was spin-coated on an8-in. silicon substrate, and the resultant structure was then heated at120 degrees Celsius for 60 seconds on a hot plate, thus forming a thinfilm of 0.4 micrometers in thickness. This thin film was exposed througha mask using a Nikon ArF excimer laser exposure system (NA=0.55).Immediately thereafter, the film was baked at 120 degrees Celsius for 60seconds on a hot plate and was developed for 60 seconds by an immersionmethod using 2.38% TMAH solution of 23 degrees Celsius, after which theresultant product was rinsed with pure water. As a result, only theunexposed portions of the resist film were dissolved into the developerand removed and a negative pattern of 0.2 micrometers line and space.(L/S) was acquired with the exposure amount of 6.4 mJ/cm². The obtainedpattern did not show pattern stripping due to insufficient adhesion anddeformation caused by swelling.

Example 9

[0148] A photoresist having the following composition was prepared. Thefollowing experiment was conducted under a yellow lamp.

[0149] (a) resin A1 (the one synthesized in the example 6) 6.84 g

[0150] (b) crosslinking agent B1 (the one described in the example 7)0.56 g

[0151] (c) photoacid generator C1(triphenylsulfoniumtrifluoro-methanesulfonato; the one described in theexample 7) 0.04 g

[0152] (d) polyhydric alcohol D1 (shown below) 0.56 g

[0153] (e) diethyleneglycol dimethyl ether 36.4 g

[0154] The prepared photoresist was spin-coated on an 8-in. siliconsubstrate, and the resultant structure was then heated at 120 degreesCelsius for 60 seconds on a hot plate, thus forming a thin film of 0.4micrometers in thickness. This thin film was exposed through a maskusing a Nikon ArF excimer laser exposure system (NA=0.55). Immediatelythereafter, the film was baked at 130 degrees Celsius for 60 seconds ona hot plate and was developed for 60 seconds by an immersion methodusing 2.38% TMAH solution of 23 degrees Celsius, after which theresultant product was rinsed with pure water. As a result, only theunexposed portions of the resist film were dissolved into the developerand removed and a negative pattern of 0.17 micrometers L/S was acquiredwith the exposure amount of 5.2 mJ/cm². The obtained pattern did notshow pattern stripping due to insufficient adhesion and deformationcaused by swelling.

Example 10

[0155] An exposure experiment was conducted in the same way as done forthe example 9 except that the photoresist was prepared using 0.56 g of acrosslinking agent B2 (shown below) instead of the crosslinking agentB1. As a result, a negative pattern of 0.21 micrometers L/S was acquiredwith the exposure amount of 5.8 mJ/cm². The obtained pattern did notshow pattern stripping due to insufficient adhesion and deformationcaused by swelling.

Example 11

[0156] An exposure experiment was conducted in the same way as done forthe example 9 except that the photoresist was prepared using 0.56 g of acrosslinking agent B3 (shown below) instead of the crosslinking agentB1. As a result, a negative pattern of 0.225 micrometers L/S wasacquired with the exposure amount of 6.0 mJ/cm². The obtained patterndid not show pattern stripping due to insufficient adhesion anddeformation caused by swelling.

Example 12

[0157] An exposure experiment was conducted in the same way as done forthe example 9 except that the photoresist was prepared using acrosslinking agent B4 (shown below) instead of the crosslinking agentB1. As a result, a negative pattern of 0.3 micrometers US was acquiredwith the exposure amount of 12.8 mJ/cm². The obtained pattern did notshow pattern stripping due to insufficient adhesion and deformationcaused by swelling.

Example 13

[0158] An exposure experiment was conducted in the same way as done forthe example 9 except that the photoresist was prepared using a crosslinking agent 85 (shown below) instead of the crosslinking agent B1. Asa result, a negative pattern of 0.35 micrometers L/S was acquired withthe exposure amount of 13.6 mJ/cm². The obtained pattern did not showpattern stripping due to insufficient adhesion and deformation caused byswelling.

Example 14

[0159] An exposure experiment was conducted in the same way as done forthe example 9 except that the photoresist was prepared using a resin A2(shown below) instead of the resin A1. The molecular weight of the resinA2 was 6200 (in terms of the molecular weight of polystyrene). Theexperiment yielded a negative pattern of 0.21 micrometers L/S with theexposure amount of 8.8 mJ/cm². The obtained pattern did not show patternstripping due to insufficient adhesion and deformation caused byswelling.

[0160] An exposure experiment was conducted in the same way as done forthe example 9 except that the photoresist was prepared using a resin A3(shown below) instead of the resin A1. The molecular weight of the resinA3 was 32500 (in terms of the molecular weight of polystyrene). In thisexperiment, 0.119 wt % of TMAH solution was used as a developer. Theexperiment yielded a negative pattern of 0.275 micrometers L/S with theexposure amount of 5.2 mJ/cm². The obtained pattern did not show patternstripping due to insufficient adhesion and deformation caused byswelling.

Example 16

[0161] An exposure experiment was conducted in the same way as done forthe example 9 except that the photoresist was prepared using a resin A4(shown below) instead of the resin A1. The molecular weight of the resinA4 was 22000 (in terms of the molecular weight of polystyrene). Theexperiment yielded a negative pattern of 0.325 micrometers L/S with theexposure amount of 3.8 mJ/cm². The obtained pattern did not show patternstripping due to insufficient adhesion and deformation caused byswelling.

Example 17

[0162] An exposure experiment was conducted in the same way as done forthe example 9 except that the photoresist was prepared using a resin A5(shown below) instead of the resin A1. The molecular weight of the resinA5 was 6100 (in terms of the molecular weight of polystyrene). Theexperiment yielded a negative pattern of 0.25 micrometers US with theexposure amount of 8 mJ/cm². The obtained pattern did not show patternstripping due to insufficient adhesion and deformation caused byswelling.

Example 18

[0163] An exposure experiment was conducted in the same way as done forthe example 9 except that the photoresist was prepared using a resin A6(shown below) instead of the resin A1. The molecular weight of the resinA6 was 8200 (in terms of the molecular weight of polystyrene). In thisexperiment, 0.119 wt % of TMAH solution was used as a developer. Theexperiment yielded a negative pattern of 0.25 micrometers L/S with theexposure amount of 4.6 mJ/cm². The obtained pattern did not show patternstripping dew to insufficient adhesion and deformation caused byswelling.

Example 19

[0164] An exposure experiment was conducted in the same way as done forthe example 9 except that the photoresist was prepared using a resin A7(shown below) instead of the resin A1. The molecular weight of the resinA7 was 6400 (in terms of the molecular weight of polystyrene). Theexperiment yielded a negative pattern of 0.19 micrometers US with theexposure amount of 3.4 mJ/cm². The obtained pattern did not show patternseparation originated from deformation and insufficient adhesion causedby swelling.

Example 20

[0165] An exposure experiment was conducted in the same way as done forthe example 9 except that the photoresist was prepared using a resin A8(shown below) instead of the resin A1. The molecular weight of the resinA8 was 5500 (in terms of the molecular weight of polystyrene). Theexperiment yielded a negative pattern of 0.21 micrometers L/S with theexposure amount of 3.6 mJ/cm². The obtained pattern did not show patternseparation originated from deformation and insufficient adhesion causedby swelling.

Example 21

[0166] An exposure experiment was conducted in the same way as done forthe example 9 except that the photoresist was prepared using a resin A9(shown below) instead of the resin A1. The molecular weight of the resinA9 was 9500 (in terms of the molecular weight of polystyrene). Theexperiment yielded a negative pattern of 0.19 micrometers US with theexposure amount of 4.0 mJ/cm². The obtained pattern did not show patternstripping due to insufficient adhesion and deformation caused byswelling.

Example 22

[0167] A photoresist having the following composition was prepared. Thefollowing experiment was conducted under a yellow lamp.

[0168] (a) resin A1 (the one synthesized in the example 6) 6.64 g

[0169] (b) crosslinking agent B1 (the one described in the example 7)0.56 g

[0170] (c) photoacid generator C2(β-oxocyclohexylmethyl-(norbornyl)trifluoromethanesulfonato; shownbelow) 0.24g

[0171] (d) polyhydric alcohol D1 (the one described in the example 9)0.56 g

[0172] (e) diethylene glycol dimethyl ether 36.4 g

[0173] The prepared photoresist was spin-coated on an 8-in. siliconsubstrate, and the resultant structure was then heated at 120 degreesCelsius for 60 seconds on a hot plate, thus forming a thin film of 0.4micrometers in thickness. This thin film was exposed through a maskusing a Nikon ArF excimer laser exposure system (NA=0.55). Immediatelythereafter, the film was baked at 130 degrees Celsius for 60 seconds ona hot plate and was developed for 60 seconds by an immersion methodusing 2.38% TMAH solution of 23 degrees Celsius, after which theresultant product was rinsed with pure water. As a result, only theunexposed portions of the resist film were dissolved into the developerand removed and a negative pattern of 0.225 micrometers L/S was acquiredwith the exposure amount of 14.4 mJ/cm². The obtained pattern did notshow pattern stripping due to insufficient adhesion and deformationcaused by swelling.

Example 23

[0174] An exposure experiment was conducted in the same way as done forthe example 9 except that the photoresist was prepared using a photoacidgenerator C3 (bis(tertiary butylphenyl)iodoniumtrifluoromethanesulfonato; shown below) instead of the photoacidgenerator C1. As a result, a negative pattern of 0.19 micrometers L/Swas acquired with the exposure amount of 10.2 mJ/cm². The obtainedpattern did not show pattern stripping due to insufficient adhesion anddeformation caused by swelling.

Example 24

[0175] A photoresist having the following composition was prepared. Thefollowing experiment was conducted under a yellow lamp.

[0176] (a) resin A1 (the one synthesized in the example 6) 6.8 g

[0177] (b) crosslinking agent B1 (the one described in the example 7)0.56 g

[0178] (c) photoacid generator C4(N-hydroxyphthalimide-p-toluenesulfonic ester; shown below) 0.08 g

[0179] (d) polyhydric alcohol D1 (the one described in the example 9)0.56 g

[0180] (e) diethylene glycol dimethyl ether 36.4 g

[0181] The prepared photoresist was spin-coated on an 8-in. siliconsubstrate, and the resultant structure was then heated at 120 degreesCelsius for 60 seconds on a hot plate, thus forming a thin film of 0.4micrometers in thickness. This thin film was exposed through a maskusing a Nikon ArF excimer laser exposure system (NA 0.55). Immediatelythereafter, the film was baked at 150 degrees Celsius for 60 seconds ona hot plate and was developed for 60 seconds by an immersion methodusing 2.38% TMAH solution of 23 degrees Celsius, after which theresultant product was rinsed with pure water. As a result, only theunexposed portions of the resist film were dissolved into the developerand removed and a negative pattern of 0.30 micrometers L/S was acquiredwith the exposure amount of 7.2 mJ/cm². The obtained pattern did notshow pattern stripping due to insufficient adhesion and deformationcaused by swelling.

Example 25

[0182] An exposure experiment was conducted in the same way as done forthe example 24 except that the photoresist was prepared using aphotoacid generator C5 (bisbenzensulfonyl-diazomethane; shown below)instead of the photoacid generator C4. Consequently, a negative patternof 0.325 micrometers L/S was acquired with the exposure amount of 7.4mJ/cm². The obtained pattern did not show pattern stripping due toinsufficient adhesion and deformation caused by swelling.

Example 26

[0183] A photoresist having the following composition was prepared. Thefollowing experiment was conducted under a yellow lamp.

[0184] (a) resin A1 (the one synthesized in the example 6) 4.65 g

[0185] (b) crosslinking agent B1 (the one described in the example 7)0.35 g

[0186] (c) diethylene glycol dimethyl ether 20 g

[0187] The above mixture was filtered by a 0.2-micrometer tetronicfilter to prepare the photoresist. This photoresist was spin-coated on a4-in. silicon substrate, and the resultant structure was then baked at100 degrees Celsius for 60 seconds on a hot plate, thus forming a thinfilm of 0.5 micrometers in thickness. The etching rate of this thin filmwith respect to CF₄ gas was measured by the reactive ion etching (RIE)apparatus DEM 451 manufactured by Anelva Corporation (etchingconditions: power=100W, pressure=5 Pa and gas flow rate=30 sccm). Theresults are shown in Table 3 below. Table 3 also shows the measuringresults for a novolak resist (PFI-15A manufactured by Sumitomo ChemicalCompany, Limited), a film coat of poly(p-vinylphenol) used as the baseresin for a KrF resist and a film coat of poly(methyl methacrylate) thatis a resin having a molecular structure which does not even have acrosslinked cyclic hydrocarbon group as comparative examples. It is tobe noted that the etching rate was standardized for the novolak resist.

[0188] The results showed that the photoresist of this invention has aslow etching rate with respect to CF₄ gas and an excellent dry etchingresistance. This means that the photoresist of this invention has a highdry etching resistance.

Example 27

[0189] An etching rate experiment was conducted in the same way as donefor the example 26 except that the photoresist was prepared using aresin A2 (the one synthesized in the example 10) instead of the resinA1. The results are shown in Table 3 below. The results showed that thephotoresist of this invention has a slow etching rate with respect toCF₄ gas and an excellent dry etching resistance. This means that thephotoresist of this invention has a high dry etching resistance. TABLE 3Etching rate (relative ratio) Example 26 1.20 Example 27 1.19Poly(methyl methacrylate) 1.9 Poly(p-vinylphenol) 1.2 Novolak resist(PFI-15A) 1

[0190] This application is based on Japanese Patent Applications Nos.H10-312171 filed on Nov. 2, 1998 and H11-087403 filed on Mar. 30, 1999,which are incorporated herein by reference in its entirety.

1. A polymer having a diol structure having a repeating unit representedby a following formula (6):

where R¹ is a hydrogen atom or methyl group, R² is a C₂-C₆ alkylenegroup and x is an alicyclic alkyl group having a diol structure.
 2. Thepolymer according to claim 1, wherein X in said formula (6) is analicyclic alkyl group having a diol structure represented by a followingformula (7), (8), (9) or (10):

where n is an integer from 0 to 3, R³ and R⁴ are a hydrogen atom ormethyl group,

where R⁵ is a hydrogen atom or methyl group,

where R⁶ is a hydrogen atom or methyl group, or

where R⁷is a hydrogen atom or methyl group.
 3. The polymer according toclaim 1, wherein said polymer has a diol structure represented by afollowing formula (11) and a weight average molecular weight of 1,000 to50,000:

where R¹ and R² are the same as those in said formula (6), X is the sameas that in any of said formulae (6) to (10), R⁸ is a hydrogen atom ormethyl group, R⁹ is a C₇-C₁₈ crosslinked cyclic hydrocarbon group havinga carboxyl group, R¹⁰ is a hydrogen atom or methyl group, R¹¹ is aC₇-C₁₃ hydrocarbon group having a hydroxyl group, R¹² is a hydrogen atomor methyl group, R¹³ is a hydrogen atom or a C₁-C₁₂ hydrocarbon grouphaving a hydroxyl group, and w, x, y and z are arbitrary valuessatisfying w+x+y+z=1, 0<w≦1, 0≦x<1, 0≦y<1 and 0≦z<1.
 4. The polymeraccording to claim 2, wherein said polymer has a diol structurerepresented by said formula (11) and a weight average molecular weightof 1,000 to 50,000.